Annexin A2 binds the internal ribosomal entry site of c-myc mRNA and regulates its translation

Abstract

The expression and localization of the oncoprotein c-Myc is highly regulated at the level of transcription, mRNA transport, translation, as well as stability of the protein. We previously showed that Annexin A2 (AnxA2) binds to a specific localization element in the 3ʹuntranslated region (UTR) of c-myc mRNA and is involved in its localization to the perinuclear region. In the present study, we demonstrate that AnxA2 binds in a Ca 2+ -dependent manner to the internal ribosomal entry site (IRES) containing two pseudoknots in the 5´UTR of the c-myc mRNA. Here, we employ an in vitro rabbit reticulocyte lysate system with chimeric c-myc reporter mRNAs to demonstrate that binding of AnxA2 to the c-myc IRES modulates the expression of c-Myc. Notably, we show that low levels of AnxA2 appear to increase, while high levels of AnxA2 inhibits translation of the chimeric mRNA. However, when both the AnxA2-binding site and the ribosomal docking site in the c-myc IRES are deleted, AnxA2 has no effect on the translation of the reporter mRNA. Forskolin-treatment of PC12 cells results in upregulation of Ser25 phosphorylated AnxA2 expression while c-Myc expression is down-regulated. The effect of forskolin on c-Myc expression and the level of Ser25 phosphorylated AnxA2 was abolished in the presence of EGTA. These findings indicate that AnxA2 regulates both the transport and subsequent translation of the c-myc mRNA, possibly by silencing the mRNA during its transport. They also suggest that AnxA2 act as a switch to turn off the c-myc IRES activity in the presence of calcium.

The cooperative folding of annexin A2 relies on a transient nonnative intermediate

“…AnxA2 is a genuinely multifunctional protein ( 1 , 2 , 3 , 4 , 5 ), involved in a variety of cellular processes ranging from membrane-cytoskeleton interactions and actin dynamics to mRNA biogenesis. The latter process involves its binding to specific mRNAs and participation in the regulation of their transport (as exemplified by c- myc mRNA ( 35 )) and/or translation (as exemplified by p53 ( 36 ) and c- myc ( 6 ) mRNAs). Moreover, AnxA2 appears to have several roles in the nucleus ( 37 ).…”

“…Annexins are defined as a family of α -helical proteins that interact with vesicles containing negatively charged phospholipids in a Ca 2+ -dependent manner ( 1 ). Annexin A2 (AnxA2) is a multifunctional protein implicated in numerous cellular processes such as signal transduction, membrane trafficking, membrane/cytoskeleton interactions, and mRNA transport and translation ( 1 , 2 , 3 , 4 , 5 , 6 ). Its involvement in multiple different functions is regulated by posttranslational modifications ( 7 ).…”

Annexin A protein family: Focusing on the occurrence, progression and treatment of cancer

“…ANXA2 regulates c-Myc expression by binding to the 5′UTR of its mRNA in a Ca 2+ -dependent manner at the two pseudoknots of the internal ribosome entry site. Thus, downstream cyclinD1, a cell cycle regulator protein, is affected, which leads to cell proliferation and a high proportion of S-phase cells (Strand et al, 2021;Sun and Zhang, 2021). The downregulation of ANXA2 stalls cells in the G 1 phase or S-G 2 /M phase in gastric cancer (Sun et al, 2013) and glioblastoma multiforme (Maule et al, 2016), respectively.…”

The flavagline FL3 interferes with the association of Annexin A2 with the eIF4F initiation complex and transiently stimulates the translation of annexin A2 mRNA

“…AnxA2 in 20 mM Tris (pH 8) was added to the RRL before the addition of the cDNA and the RRL constituted 63% of the assays. The reaction was performed as previously described (Strand et al, 2021). Incorporated [ 35 S]-Met into the AnxA2 protein and total radioactivity in the reaction mixture were measured in a Packard liquid scintillation counter.…”